Methods for altering the configuration of electrically conductive turns of inductivedevices



Oct. 29, 1968 METHODS FOR AL ELECTRICALLY CONDUCTIVE TURNS OF INDUCTIVEDEVICES a y 1 ms 6 T r n m 4 mm W M5 m n I w m H J 70 Original Filed JulfA/[PGY SOURCE Oct. 29, 1968 METHODS FOR AL 5 Sheets-Sheet 2 INDUCTIVEDEVICES Original FiledJuly 28, 1966 sen;

m M N a n. E r V CL 0 W. n M a w A J Y B m M R 544.1%)! zwl z a W )6 IPI I W/w r 6 Sheets-Sheet 5 J. E. LARSEN METHODS FOR ALTERING THECONFIGURATION OF ELECTRICALLY CONDUCTIVE TURNS OF INDUCTIVE DEVICES &M%17M Original Filed July 28. 1966 Oct. 29, 1968 United States Patent 0.

3,407,488 METHODS FOR ALTERING THE CONFIGURATION F ELECTRICALLYCONDUCTIVE TURNS OF INDUCTIVE DEVICES John E. Larsen, Fort Wayne, Ind.,assignor to General Electric Company, a corporation of New York Originalapplication July 28, 1966, Ser. No. 568,588. Divided and thisapplication Oct. 12, 1967, Set. N 0. 674,804

19 Claims. (Cl. 29-596) ABSTRACT OF THE DISCLOSURE In altering theconfigurations of electrically conductive turns carried in the slots ofa magnetic core, a rigid electrical conductor is supported in the slotsnext to the turns and connected across output terminals of an electricalsurge source. A surge is injected from the source into the rigidconductor to generate an electrical energy surge in the turns, creatingforces of sufiicient magnitude to change the cross-section of a majorityof the turns carried by the slot. The majority of the turns in the slot,altered into non-circular cross-section configurations, and their finalrelative turn positions in the slots are primarily determined by forcesacting on the turns of approximately 10,000 pounds per square inch ormore thereby producing compacted turns in the slot having a slot spacefactor in excess of 60%. Not only unusually high slot space factors areprovided for the conductors, but in addition, the turns are wedgedtightly within the slot so that they may be retained therein withoutneed for auxiliary holding devices during subsequent stages offabrication.

Cross-reference to related application This application is a division ofmy co-pending application, Ser. No. 568,588 filed July 28, 1966.

Background of the invention This invention relates generally to improvedmethods for altering the configuration of electrically conductive turns.More particularly, the invention relates to improved methods forpressing back conductor turns rela tive to their initial position inmagnetic cores.

Electromagnetic devices such as magnetic cores used in electricalmotors, generators and the like customarily incorporate one or moreelectrical coils wound from a number of relatively flexible insulatedconductor turns.

The manufacture of these devices has in the past posed U certainproblems, especially in the development of wound coils in the magneticcores.

One of the manufacturing techniques used to place electrical conductorturns in the slots of magnetic cores during the development of woundcoils is that of winding conductor turns directly into the slots andthereafter compacting or pressing back the turns toward the slotbottoms. Another technique commonly used to place electrical conductorturns in core slots is that of forming a wound 'coil of conductor turnsat one location and then transferring the wound coil into the coreslots. However in either technique it is exceedingly difficult toachieve slot space factors above 60%. Accordingly, the number of turnswhich can be placed in any one slot is limited when using thesetechniques. Even with conventional mechanical press-back equipmentcurrently available, it is unusually difiicult to increase the slotspace factors above 75%, when using conventional round or nearly roundconductors, without appreciable problems, such as causing undue damageto the conductor insulation.

It is, therefore,desirable to be able to achieve higher slot spacefactors and above) than were heretofore feasible, while avoiding thewell-known difiiculties involved with the use of conventional mechanicalpressback equipment (e.g., expense, lack of speed, and damage to wireinsulation). This is especially desirable as it will allow moreconductor turns to be placed in any one slot and will therefore allowrelatively inexpensive aluminum conductor wire to be more widely used ascompared with copper wire for a given core design. More turns ofaluminum than copper conductors are required, of course, for a givenslot volume to achieve the same rating in view of the differences intheir electrical conductivity properties. Further, it is desirable to beable to wedge conductor turns into the slots of magnetic coresregardless of the slot configuration, thereby to retain the turns in theslots without the need for auxiliary holding means during subsequentstages of fabrication.

United States Patents 3,333,327-3, 333,330 inclusive and 3,333,335 allissued Aug. 1, 1967, which are assigned to the same assignee as thisapplication, disclose novel and unique ways of compacting or otherwisetransforming coils in electromagnetic devices involving the use ofelectrical energy, in one form or another. It is highly desirable tomake use of the electrical energy approach to accomplish the desiredresults set forth above.

Accordingly, it is a general object of the instant invention to provideimproved methods for altering the configurations of conductive turnsuseful in electrical inductive devices so as to achieve at least some ofthe desirable results mentioned above.

A more specific object of the present invention is the provision ofimproved methods of compacting and pressing back conductor turns in theslots of magnetic cores thereby to pack a greater number of turns intothe slots in a most expeditious and efficient manner.

Another specific object of the instant invention is the provision ofimproved methods for wedging conductor turns into the slots of magneticcores to provide slot space factors in excess of 60%.

A further object of the present invention is to provide novel andimproved methods for altering the overall configuration of wound coilscarried in coil accommodating slots of magnetic cores and developingthese wound coils in the slots; the altering and developing includingfor example, pushing back the end turn portions of a coil, compactingthe turns at the side portions and end turn portions, moving the sideturn portions toward the slot bottoms, and changing the cross-section ofthe side turn portions.

Summary of the invention In carrying out my invention in one form, Iprovide an improved method of altering the configuration of electricallyconductive turns comprising at least a portion of electrical coilscarried in coil accommodating slots of a magnetic core. In oneillustrated exemplification, rigid conductor means is supported inselected coil accommodating slots of the magnetic core, corresponding inthe exemplification to the slots accommodating at least one of the sideportions of a wound electrical coil. The rigid conductor means iselectrically connected across the output terminals of an electricalenergy surge source, and a surge of electrical energy is injected intothe conductor means, thereby establishing a transient magnetic field andelectromagnetic forces to press the electrically conductive turns backin their coil accommodating slots. The surge may be of sufiicientmagnitude to change the cross-section of a majority of the individualconductor turns carried in a slot.

In accordance with a more specific aspect of my invention, nonmagneticelectrically conductive material capable of conducting eddy currents issupported adjacent the entrance of a coil accommodating slot havingconductor turns and rigid conductor means therein. The material is alsosupported adjacent the end turn portions of the coil, therebyestablishing forces during the injection step to rigidly support theconductor means in the slots and to press-back the coil end turnportions.

The methods of turn alteration in accordance with my invention areefiicient and economical, and as well provide high slot space factorssince the forces generated to effect press-back may be great enough tochange the cross-section of at least a majority of the conductor turnsin a slot. By changing the cross-section of the conductor turns, agreater compaction of the turns in the slots is possible, and a greaternumber of turns may therefore be accommodated in the slots. Thus, theavailability of high slot space factors provided by my methods willallow aluminum conductor wire to be used, if so desired. A furtheradvantage of my method is that upon a change in cross-section of theconductor turns, the turns will be wedged into the slots. The turns willthereby be retained in the slots without the need for auxiliary holdingmeans during subsequent stages of fabrication of inductive devicesutilizing the magnetic cores. In addition, by the practice of my method,the conductor insulation is not adversely alfected as there is nophysical contact with the wire insulation during the alteration ordeveloping operations.

The subject matter which I regard as my invention is particularlypointed out and distinctly claimed in the concluding portion of thisspecification. The invention itself, however, together with furtherobjects and advantages thereof may be best understood by reference tothe following description taken in conjunction with the accompanyingdrawings.

Brief description of the drawings FIGURE 1 is an end view of the statorcore with two coil groups shown in the coil-accommodating slots of thecore, and including first exemplified apparatus for carrying out theturn altering or developing methods of my invention, the apparatus ofthe exemplification including rigid conductor means supported inselected coil-accommodating slots of the core and a rigid structure ofnonmagnetic electrically conductive material disposed in the bore of thecore;

FIGURE 2 is a fragmentary perspective view of the stator core andapparatus illustrated in FIGURE 1, showing schematically the connectionof the rigid conductor means to a source of electrical energy, and withone wound coil illustrated in initial, intermediate and final altered ordeveloped positions in the core;

FIGURE 3 is an enlarged fragmentary view of one coil-accommodating slotof the stator shown in FIGURES 1 and 2, illustrating the distribution ofthe individual conductors after insertion of a coil side portion intothe slot and prior to the altering or development of the conductor turnsin the slot, with the rigid conductor means in 'a first position in theslot relative to the conductor turns and the electrically conductivenonmagnetic material;

FIGURE 4 is an enlarged fragmentary view of the coil-accommodating slotand apparatus illustrated in FIG- URE 3, the view of FIGURE 4 showingthe compaction and change in cross-section of the conductor turnsachieved by the present invention and also showing the rigid conductormeans in its supported position;

FIGURE 5 is a perspective view, partially in crosssection, of one formof apparatus useful in practicing the method of my invention;

FIGURE 6 is a vertical sectional view taken substantially on the planeof the line 66 of FIGURE 5;

FIGURE 7 is a vertical sectional view taken substantially on the planeof the line 7-7 of FIGURE 6;

FIGURE 8 is an enlarged fragmentary view of one coil-accommodating slotillustrating the final distribution of the individual conductor turnscarried therein when 4 practicing the method of my invention with theapparatus illustrated in FIGURES 5-7; and

FIGURE 9 is a partial perspective view, partially in vertical section ofone coil-accommodating slot of a stator, and still another exemplifiedform of apparatus useful for practicing the method of my invention.

Description of the preferred embodiments For the purpose of explainingthe principles of my invention, I have illustrated in FIGURES 1-4inclusive various aspects of my improved method as applied to a statorcore generally denoted by reference numeral 10. The core 10 carries twocoil groups 12 and 14 comprising the main running winding for a two-poleinduction motor. It will be noted that each coil group 12 and 14includes five wound coils, each coil including a plurality ofindividually wound insulated flexible conductor turns. The exemplifiedstator core 10 includes twenty-four coil-accommodating slots foraccommodating the wound coils. In a stator core of the type illustratedin FIGURE 1, opposed coil-accommodating slots such as 16, 18, and 22,24, and 26, 28 each carry one Wound coil therein. As will be noted, Ihave illustrated in cross-section the individual conductor turns 21 ofthe one wound coil 20 carried in the stator core coil-accommodatingslots 16 and 18.

In the illustrated exemplification, the one wound coil 20 includes fortyindividual conductor turns 21, the side portions of the coil 20 beingaccommodated in the slots 16 and 18 and the end turn portions projectingaxially beyond the stator end faces 19. In addition, the three pairs ofslots 16, 18; 22, 24; and 26, 28 each carry coils composed of arelatively large number of individual conductor turns. Further, the slotpairs 22, 24 and 26, 28 are adapted to receive start windings includingadditional conductor turns as well as the conductor turns of the woundcoils comprising a portion of the main or running winding. Accordingly,it is most desirable to press-hack the coil side portions of the coilscarried in these three pairs of slots in order to accommodate themaximum number of turns. As explained above, it is desirable to achievethe highest possible slot space factor, or the greatest ratio of slotarea actually filled with conductor turns as compared to the availableslot area so as to accommodate the maximum number of turns therein,while not damaging the conductor insulation. In FIGURE 3, I haveillustrated the forty conductor turns 21 of the wound coil 20 located inthe slot 18 after the side portions of the wound coil have been insertedin the slot and prior to the altering or developing method of myinvention. As will be noted in FIGURE 3, the conductor turns 21 areloosely located in the slot 18, with voids or spaces therebetween, andhence the slot space factor is relatively low. It is anticipated, forexample, that if the wound coil 20 were placed in the stator core 10 bya machine, such as is disclosed in the United States Patent 2,934,099granted to Lowell M. Mason on Apr. 26, 1960, the slot space factor wouldbe in the neighborhood of 60%.

Since it is desirable to compact the individual conductors in the slot18 in order to achieve a slot space factor in the range of to percent,according to one form of my invention, I support rigid conductor meansgenerally denoted by reference number 22 in the slot 18 between the slotentrance 25 and the slot bottom wall 31. The rigid conductor means 22 isthereby in inductively or transformer-coupled relationship with theconductor turns 21 located in the slot 18. The coil 20 provides a closedpath for the flow of induced current. In the exemplification, I connectthe rigid conductor means 22 across the output terminals 27 and 29 of anenergy surge source generally denoted by reference numeral 32.

The energy surge source 32 used in the illustrative exemplification ofthe invention may be any suitable source, such as one of the capacitordischarge energy source disclosed in the aforementioned U.S. patentsissued on Aug. 1, 1967, with a capability of supplying an electricalpower surge of sufiicient magnitude. Accordingly, when the surge source32 is energized, an energy surge of preselected intensity is injectedinto the rigid conductor means 22 thereby establishing a transientmagnetic field about the rigid conductor means, and inducing currentflow in the Wound coil 20. It is believed that the instantaneous currentflow through the wound coil 20 establishes a transient magnetic fieldthereabout which interacts with the field about the rigid conductormeans 22, creating electromagnetic forces which force the conductorturns 21 toward the bottom 31 of the slot 18.

The finally developed or altered configuration of the turns isillustrated in FIGURE 4. It will be understood that if the electricalpulse or surge of energy injected into the rigid conductor means 22 isof great enough magnitude, it will force the conductor turns of the coil20 against the slot bottom 31 with suflicient force to change thecross-section of at least the majority of the conductor turns carried inthe slot. This final conductor configuration will be seen in FIGURE 4.Further, after the core is saturated, it is believed that additionalcompaction of the coil is achieved by attractive forces between theindividual coil turns. It is also believed that such core saturationoccurs almost instantaneously, or during the initial portion of theenergy surge. Typically, it has been estimated that in order to changethe cross-section of round aluminum conductors, approximately 10,000pounds per square inch must be applied against the conductors, and inorder to change the cross-section of round copper conductors,approximately 18,000 pounds per square inch must be appliedthereagainst.

The forces generated against the conductor turns in the stator slots bythe exemplification is of sufficient magnitude to change thecross-section of at least a majority of the conductors in the slot andhence achieve an unusually high slot space factor, well over 60%. Statedotherwise, the voids or spaces between the conductor turns in the slotare virtually eliminated by the resulting surface-tosurface contactbetween the previously round conductors as the conductors changecross-section in response to the force thereagainst. Further, the changeof cross-section is attained without deleteriously affecting the qualityof the insulation covering the wire. It should also be understood thatthere is a wedging effect produced by this change of cross-section ofthe conductors, wherein the conductors are wedged in the slot. Theconductor turns will therefore be retained in the slot without the needfor auxiliary holding means to retain them in the slot as the statorcore is transferred during subsequent stages of fabrication.

In applying my invention to a two-pole stator core similar to the oneillustrated in FIGURES l and 2, and particularly to a wound coilcomprised of forty conductor turns and wound to an original slot spacefactor of 63 percent carried in such a stator core, an energy surge of2,767.5 joules at 3000 volts was injected into the rigid conductor means22 supported in the coil-accommodating slot 18. The resulting currentflow through the rigid conductor means was approximately 75,000 amperes(peak) and the final slot space factor, as illustrated in FIGURE 4 wascalculated to be approximately 90%. The conductor turns in this instancewere 0.0508 inch diameter aluminum wire insulated with polyvinyl formalor Formex insulation, and the rigid conductor means 22 illustrated inFIGURE 3 was 0.096 by 0.160 inch rec tangular insulated copper.

In applying my invention to another stator core 10, rigid conductormeans similar to means 22 was used to compact and alter theconfiguration of 51 conductor turns carried in a stator slot. Theconductor turns in this instance were 0.0427 inch diameter copper wireinsulated with Formex insulation, and the energy injected into theconductor means 22 was approximately 4,590 joules at 3000 volts. Theresulting current flow in the rigid conductor means was 9,000 amperes(maximum) and the resulting compaction and alteration of the conductorturns ,carried in the slot was similar to the results illustrated inFIGURE 4, a slot space factor of approximately being attained.

Referring again to FIGURES 1-4 inclusive in order to explain how themethod described above was carried out in actual practice, I will nowmore fully describe the rigid conductor means 22 and the manner in whichit was supported in the stator slots. The rigid conductor means 22, asillustrated in FIGURE 2, comprises a generally U-shaped member 23 ofelectrically conductive material, the material actually used beingcopper in this instance. The member 23 includes two opposed leg portions28 and 30 connected by a bi'ght portion 33. The leg and biglit portionsare generally rectangular in cross-section (in one exemplification 0.096by 0.160'inch). The opposed leg portions 28 and 30 of the member 23' areshaped to fit into the core slots, and are moved into opposedcoilaccommodating slots 26 and 28 axially from one end of the stator.These slots 26 and 28 accommodate the side portion 36 of the Wound coil20 therein. At each free end of the leg portions 28 and 30 there aresuitable terminals 34 to enable the structure 23 to be connected acrossthe output terminals 27 and 29 of an electrical energy surge source 32as illustrated in FIGURE 2.

Referring further to FIGURE 2, it will be observed that the wound coil20 is illustrated schematically in full lines in its final locationrelative to the core 10, with the coil side portions 36 pressed towardthe slot bottoms 31 of the coil-accommodating slots 26 and 28 and withthe end turn portions 38 pressed back towards the stator core end faces19. I have also shown the initial location of the wound coil 20 in theslots 26 and 28 at 42, and an intermediate location at 44. The threelocations of the coil 20 in the slots 26 and 28 are shown in this mannerin order to illustrate a further aspect of my method.

The initial designation 42 denotes the location of the coil when it isplaced in the slots by a suitable machine for that purpose. Theintermediate designation 44 denotes the coil location after an initialenergy surge is injected into the structure 23. When the initial energysurge of energy is injected into the member 23 from surge source 32, thecoil 20 is moved to the intermediate position 44 with the coil sideportions 36 adjacent the slot bottoms; however, the coil end turnportions 38 are only slightly affected. The wound coil 20 is thenconnected across the output terminals 27, 29 of the surge source 32 andthe terminals 34 of the member 23 are shorted together to provide aclosed electrical path in the member. With a rigid structure 46 ofelectrically conductive nonmagnetic material capable of conducting eddycurrents disposed in the stator bore 48, a surge of energy is theninjected directly into the wound coil 20. Electromagnetic forces arecreated between the coil end turn portions 38 and the structure 46, andthe coil end turn portions 38 are moved to their final location adjacentthe stator end faces 19, as shown in FIGURE 2. The side portions 36 ofthe coil 20 will also be further compacted at this time.

As will be seen in FIGURES 1 and 2, the structure 46 comprises agenerally cylindrical member shaped to fit the stator bore 48 andincludes an insulative layer 50 for electrically insulating thestructure 46 from the conductor windings. The insulative layer mayeither be a separate hollow member or integrally formed on the surfaceof the structure 46, as desired. Since the structure 46 is capable ofconducting eddy currents, when current flows in the wound coil 20, aninteraction of electromagnetic forces takes place between the coil endturn portions 38 and the structure 46 to press the end turn portions tothe position illustrated in FIGURE 2.

It will be understood that the U-shaped member 23 may be mechanicallysupported in the stator core 10 by suitable supporting means, if sodesired. I have found, however, that the structure 46 comprises meansfor supporting member 23 in the coil-accommodating slots 26 and 28. Thesupport is achieved by electromagnetic forces established between themember 23 and the conductor turns and the member 23 are movable, theforces will balance or equalize when the turns have been pressed towardthe slot bottom31 as far as possible and when the member 23 is at apredetermined location between the conductor turns 21 and the structure46, as illustrated in FIGURE 4. Of course, it will be understood thatthe force generated between the member 23 and the'conductor turns 21 ofthe coil 20 forces the conductor turns downwardly toward the slot bottom31 as well as balancing the opposing force generated between the'member23 and the structure 46.

Whi.e I have described my method as it is practiced by the exemplifiedapparatus of FIGURES 1-4, the method may also be practiced by theapparatus illustrated in FIGURES 8 inclusive. I have shown therein asecond type of rigid conductor means for practicing the method.Referring first to FIGURE 5, wherein like numerals refer to like parts,the second form of rigid conductor means is generally denoted byreference numeral 52 and includes a rigid conductor carrying structureor fixture 54 shaped to fit the bore of a stator such as the stator 10.The structure 54 is a generally cylindrical, elongate member constructedof electrically conductive nonmagnetic material 56 capable of conductingeddy currents and has portions encapsulated by suitable insulatingmaterial 58. The structure 54 carries three pairs of rigid conductorbars, the pairs being generally denotedby the reference numerals 60, 62,64, respectively. Each pair of conductor bars comprises a generallyU-shaped member whichv includes leg portions 66 and 68 and aninterconnecting bight portion 70, as will be observed, for example, inFIGURE 6. The leg portions 66 and 68 extend radially outwardly of andaxially along the carrying structure 54, being mounted in insulatedslots 72 which extend axially along the structure as will be seen inFIGURE 8, for example. Further, each leg portion of the three pairs ofconductor bars includes an upstanding portion 74 of generally oblongcross-section, shaped to fit axially into a stator corecoil-accommodating slot such as the slot 76 illustrated in FIGURE 8.Each upstanding portion 74 is insulated as at 80, to insure against thepossibility of its shorting with the conductor turns 82, carried in theslot 76.

Referring again to FIGURE 5', it will be seen that a shunt ring 84 ismounted in the structure 54 and retained by the encapsulating insulation58. The shunt ring 84 is in contact with each pair of conductor bars,thereby to provide a parallel electrical conduction across the threepairs 60, 62, and 64 of the conductor bars. Inwardly disposed portions86 and 88 of the shunt ring 84 haveterminals 90 and 92 respectivelyextending axially therefrom. The terminals 90 and 92 are supported in arounded end portion of the structure 54 generally denoted by referencenumeral 94, and rigidly maintained by the insulation 58, with portionsof the terminals extending outwardly of the end portion 94 to enableelectrical connections to be made therewith. The rounded end portion 94isprovided'to enable the structure .54 to be easily moved intothe boreof the. stator core 10, as it will push back theend turns which mayblock the bore.

The rigid conductor carrying structure or fixture 54 is mounted'as bymounting screws 98 and 100 on a mounting block 102, thereby beingsituated to receive the stator core in coil altering position thereon.-Thus, the stator core 10 may be moved axially onto the structure 54,with the pairs of conductor bars 60,62, and 64 thereby being moved ontoopposed pairs of coil-accommodating slots 76 carrying the side portionsof wound coils therein. The conductor bars are supported in the statorslots 76, when the stator core 10 is in place, by the structure 54 whichlies adjacent to the entrances of the slots.

In using the apparatus illustrated in FIGURES 5-8 inclusive to practicemy method, an energy surge is injected into the pairs of conductor barsthrough the terminals 9 0 and 92 and shunt ring 84; The three woundcoils, carried in the three pairs of sloits in which the three pairs ofconductor bars 60, 62, and6-flare supported, are connected to provide aclosed path for the flow of induced current. Electromagnetic forces arethus created between the conductor bars and these wound coils therebycompacting the coil side portionstoward the bottoms of these slots, asillustrated in FIGURE 8. It will be noted that the cross-section of thecoil side portions is changed during the coil compaction therebyachieving a high space factor as contemplated by my method. Further, itwill be understood that by using the apparatus of FIGURES 5-8 topractice my method, the configuration of three wound coils may bealtered (i.e., the coils developed) at the Sametime. Thus, the threewound coils carried in the slot pairs in which it is most desirable toattain'high space factors (i.e., the slot pairs which receive thegreatest total number of conductor turns therein) may be compacted inone quick, efficient operation. Further, the end turn portions of thewound coils will normally be generally adjacent the electricallyconductive nonmagnetic portion 56 of the structure 54 when the statorcore is mounted on the structure 54, and hence the end turn portions ofthe coils will also be compacted and forced back toward the stator faceswhen using the apparatus of FIG- URES 58 to practice my method.

, Referring now to FIGURE 9, it will be observed that yet anotherexemplified apparatus for practicing my above described method isillustrated. I have shown in FIGURE 9 another rigid conductor means, inthis instance, generally denoted by reference numeral 106. The means 106comprises a plurality of flexible electrically conductive wires 108rigidly mounted or contained in a rigid insulator structure 110. Theinsulator structure 110 is shaped to fit axially into acoil-accommodating slot such as the slot 112 and may be constructed of asuitable thermosetting material such as thermosetting epoxy resin, whichwill normally be formed about the plurality of conductive wires 108 inorder to rigidly support the wires 108 in insulated spaced apartposition. Thestructure 110 further includes a stiffening means in theform of a generally T-shaped member 116 suitably attached to the bottomof the structure. The stiffening means 116 is provided in order toinsurethat when forces are generated between the rigid conductor means106 and the conductor turns carried in the slot 112, the conductor means106 will remain rigid. While'I have shown only one rigid conductor means106 supported in'one coil-accommodaL ing slot 112, it 'will beunderstood that any desired mum'- ber of such means 106 may be supportedin various of the slots of a stator core at one time. It would normallybe the case, forexample, that two such structures'llll would besupported in two opposed slots of a core carrying therein the two sideportions of one'wound coil by supporting means (not illustrated) at oneend of the structures adjacent the end face of the stator cor'e.

In actually practicing uniform of my invention,'rigid conductor means inthe general form-of the apparatus illustrated in FIGURES 58 inclusivewas' used.-"The structure 54 was disposed in a stator'b'o re, with thethree pairs'of conductorbars 60, 62; and 64 being rigidly sup ported inthree pairs of coil-accommodating slots of a.

two-pole stator containing 0.05 08 inch di arn'e'ter' conduc tor turnsof aluminum conductor"wire insulated with Formex insulation. Two'surges"or electrical energy at approximately4',59 0 joules at 3000 volts wer einjected into the rigid conductor bars, with 115,000 amperes (maximum)flowing through the/bars on the' first pulse,

and 107,000 amperes (maximum) flowingthrough the bars on the secondpulse. A third pulse was then injected into the bars at an energy levelof approximately 5,655 joules at 3300 volts, producing 115,000 amperes(maximum) therein. The rigid conductor means or bar pairs 60, 62, and 64were then disconnected from the energy surge source, and three woundcoils carried in the three pairs of coil-accommodating slots seriallyconnected together and connected across the energy surge source 32. Withthe three pairs of conductor bars 60, 62, and 64 connected to provide aclosed path for the flow of induced current, an energy surge ofapproximately 5,100 joules at 1000 volts was injected into the threewound coils. By the above steps, the side portions of the three seriallyconnected wound coils were compacted in their stator slots, thecross-section of a majority of the conductor turns in these slots waschanged, and a relatively high space factor (approximately 79%, 73% and70% for the outer, intermediate and inner coils respectively) wasachieved. Further, the end turn portions of the three wound coils werepressed back toward the stator end faces, and the three wound coils werethereby fully developed into a final desired configuration.

In view of the foregoing, it will be apparent that by my improvedmethods it is not only possible to move individual conductors formingthe side portions of wound coils toward the bottom of stator core slotscarrying these wound coils, but it is also possible to compact them withsufficient force to actually change the cross-section of a majority ofthe conductors, thereby achieving unusually high slot space factors.Further, these high slot space factors are accomplished without applyingany mechanical means directly to the conductor wires for aifecting therequired compacting forces, and hence the wire insulation is not damagedin practicing my invention. Another advantage of the invention is thatthe end portions of the wound coils may be pressed back concurrently,with the compaction of the side portions, and that the side portions maybe wedged into the stator slots. Accordingly, I have found that by mymethods I am able to accomplish coil alteration or development in amagnetic core in a rapid and economical manner, and am able in manyapplications to substitute relatively less expensive insulated aluminumconductor wire for copper wire as well as produce a device of improvedstructure.

Although the principles of my invention may be used advantageously forthe development or alteration of wound coils in a stator core, it willbe apparent to those skilled in the art that the principles of theinvention may also be employed effectively in other inductive deviceswhere it is desirable to alter the configuration of electrical coils.

While in accordance with the patent statutes, I have described What atpresent are considered to be preferred forms of my invention, it will beobvious to those skilled in the art that modifications may be madethereto without departing from the invention. It is, therefore, intendedin the appended claims to cover all such equivalent modifications andvariations that fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A method of developing an electrical winding carried incoil-accommodating slots of a magnetic core having a bore, the windingincluding at least one wound coil comprising a number of conductor turnsand having first and second side portions at initial locations in twocoilaccommodating slots of the core and two end turn portions extendingbeyond opposed end faces of the core, the method comprising the stepsof: supporting first and second rigid conductor means in the twocoil-accommodating slots of the core respectively adjacent the first andsecond coil side portions, each conductor means being in close proximityto the conductor turns of its respectively adjacent coil side portion inthe slots; electrically connecting the first and second conductor meansacross output terminals of an electrical energy surge source; andinjecting a surge of electrical energy into the first and secondconductor means, and establishing a transient magnetic field about thefirst and second conductor means, thereby inducing a surge ofcurrent-flow in the wound coil and creating electromagnetic forces tomove the two side portions away from their initial locations in theslots.

2. The method of claim 1 wherein the step of injecting a surge ofelectrical energy into the first and second conductor means includesinjecting a surge of electrical energy therein of sufiicient magnitudeto create electromagnetic forces which will cause the cross-section ofat least some of the conductor turns to be changed.

3. The method of claim 1 wherein the step of supporting first and secondrigid conductor means in the two coil-accommodating slots includesdisposing a rigid nonmagnetic electrically conductive structure capableof conduting eddy currents in the bore of the magnetic core, therebycreating generally equal and opposing forces between the first andsecond rigid conductor means and their respectively adjacent coil sideportions and between the first and second rigid conductor means and thestructure When a surge of electrical energy is injected into the firstand second rigid conductor means.

4. The method of claim 1 wherein the step of supporting first and secondrigid conductor means in the two coil-accommodating slots includesrigidly supporting the first and second rigid conductor means in the twocoilaccommodating slots by disposing a supporting structure in the boreof the core, the supporting structure being in supporting contact withthe first and second rigid conductor means.

5. The method of claim 1 wherein the step of supporting first and secondrigid conductor means in the two coil-accommodating slots includessupporting the first and second rigid conductor means in the twocoilaccommodating slots by providing means for supporting the first andsecond rigid conductormeans at one end thereof.

6. The method of claim 1 wherein the step of supporting first and secondrigid conductor means in the two coil-accommodating slots of the coreincludes moving the rigid conductor means into the coil-accommodatingslots in such a manner as to mechanically push back at least a portionof the wound coil conductor turns.

7. A method of altering the configuration of electrically conductiveturns comprising at least a portion of an electrical coil carried incoil-accommodating slots of a magnetic core, the coil-accommodatingslots having an open entrance and a closed bottom, the method comprisingthe steps of: disposing rigid conductor means in a coil-accommodatingslot having electrically conductive turns carried therein, andgenerating a surge of electrical energy in at least the rigid conductormeans accommodated in the slot, establishing a transient magnetic fieldthereby to create electromagnetic forces and press the electricallyconductive turns toward the closed bottom of the coil-accommodating slotaway from the rigid conductor means.

8. The method of claim 7 including the additional step of disposingnonmagnetic material, capable of conducting eddy currents, adjacent theslot entrance of said coilaccommodating slot, thereby to support therigid conductor means in the slot.

9. The method of claim 8 including the further step of supportingnonmagnetic material, capable of conducting eddy currents adjacent otherportions of said electrical coil, thereby to press back these otherportions of said electrical coil.

10. The method of claim 8 wherein the step of disposing rigid conductormeans in a coil-accommodating slot includes supporting the rigidconductor means in 11 i said coil-accommodating slot between theelectrically conductive turns and the slot entrance.

11. The method of claim 10 wherein the step of supporting the rigidconductor means between the electrically conductive turns and the slotentrance includes rigidly supporting the rigid conductor means betweenthe electrically conductive turns and the nonmagnetic material bybalanced and opposing electromagnetic forces generated between the rigidconductor means and the nonmagnetic material and between the rigidconductor means and the electrically conductive turns when the transientmagnetic field is generated.

12. The method of claim 7 wherein the step of injecting a surge ofelectrical energy in the rigid conductor means includes injecting asurge of electrical energy therein of sufficient magnitude to change thecross-section of a majority of the electrically conductive turns carriedin said coil-accommodating slot, and thereby wedging the electricallyconductive turns in said coil-accommodatin g slot.

13. The method of claim 7 wherein the step of disposing rigid conductormeans in a coil-accommodating slot includes disposing electricallyconnected rigid conductor means in two coil-accommodating slots carryingan electrical coil; the step of injecting a surge of electrical energyin a rigid conductor means including electrically connecting first endsof the two rigid conductor means in circuit with the output terminals ofan electrical energy surge source, and energizing said electrical energysurge source.

14. The method of claim 7 wherein the step of disposing rigid conductormeans in a coil-accommodating slot includes rigidly supporting the rigidconductor means in the coil-accommodating slot by providing a supportingstructure thereof adjacent the slot entrance in supporting contacttherewith.

15. The method of claim 7 wherein the step of disposing rigid conductormeans in a coil-accommodating slot includes moving the rigid conductormeans into the coilaccornmodating slot in such a manner as tomechanically push back at least a portion of the electrically conductiveturns.

16. A method for producing high slot space factors of electricallyconductive turns disposed in slots of a 1.2. .2 magnetic core, themethod comprising the steps of: generating an electrical energy surge inthe turns of sufficient magnitude to establish a transient magneticfield and electromagnetic forces acting upon the turns; and altering thecross-section of the majority 0f the turns carried in theslots intonon-circularconfigurations, and changing the relative positions'thereof.bythe forces acting thereon to produce slot space factors for the turnsin the neighborhood of 80% or more. 7 I

17. The method'of claim 16 in which the changed non-circularcross-section configurations and altered relative turn positions areprimarily determined by forces acting on the turns of approximately10,000 pounds per square inch or more.

18. A method for altering the configuration of electrically conductiveturns disposed in slots of a magnetic core, the method comprising thesteps of: disposing electrically conductive turns in slots of amagneticcore, changing a majority of the turns into non-circular crosssectionconfigurations as the turns are disposed in the slots and altering theirrelative positions with respect to one another by generating a surge ofelectrical energy in the turns thereby creating transient fields andelectromagnetic forces of sufiicient magnitude acting on the turns toproduce compacted turns in the slots having slot space factors in excessof 60%.

19. The method of claim 18 in which the forces acting on the turnsproduce compacted turns tightly wedged in the slots which tend to retaintheir relative turn positions during subsequent operations performed onthe magnetic core.

References Cited UNITED STATES PATENTS Linkous 29-205 JOHN F. CAMPBELL,Primary Examiner.

J. L. CLINE, Assistant Examiner.

